Instructions
Travel from the back of the temple to the dark area you see in the distance. Go across the bridge you find here to reach the cave where this creature dwells.
Stay on the back of your horse as this monster has a homing attack that will do major damage to you if you are on foot. With the horse you have enough speed to dodge its attacks.
Lead the monster outside and lure it over one of the geysers that cover the landscape. Shoot arrows at the monster to get its attention and position the monster precisely over a geyser.
Shoot the bottom of the monster's feet as soon as the geyser blast hits it. Doing this will flip the monster over and allow you to get access to it. As soon as the monster falls on its side, get in close, jump off your horse and start climbing up the turtle's stomach.
Climb onto the turtle's shell as it stands up, then follow the route along the spikes on its back until you reach its head. Stab the turtle six times in the head to kill it.